In recent years, in an automobile outside plate coating, a line coating is carried out with a 2C-1B finishing in the form of the combination of acryl polyol with a melamine resin. A lot of a solvent is released to air from this line coating, and in addition, there used to be involved the problem that an earth warming phenomenon attributable to the generation of a lot of carbon dioxide is accelerated as well by subjecting this discharged solvent to a burning treatment.
A shift to an aqueous coating is widely investigated with mainly a base coat. In a clear coat, a high quality appearance and various high grade performances for a paint film such as a durability are required.
A water base paint, a powder paint, and a UV-curing series paint have widely been investigated. It may be said that a solvent reduction in a conventional type resin will be the shortest way.
However, in the case where a shift to a lower molecular weight is carried out in order to attempt a shift to a high solids content in the combination of a conventional acryl polyol-melamine resin, the content of a hydroxyl group has to be raised in order to cover a curing shortage. A shift to a low viscosity can not necessarily be achieved with this means, and in addition, a paint obtained by curing a resin having a high hydroxyl number with a melamine resin brings about the result that a resistance to acid is extremely lowered. In addition thereto, there was involved the inconvenience that the shift to a low viscosity was accompanied with the notable generation of sagging on a vertical plane in coating.